Developer documentation for the development of plugins

Created by: stefanoborini

Fixes #141 (closed)

doc/source/design.rst

@@ -5,7 +5,6 @@ The application is based on five entities, as written in the introduction:
 
 - Multi Criteria Optimizer (MCO)
 - DataSources
-- Key Performance Indicator (KPI) Calculators
 - Notification Listeners
 - UI Hooks
 
@@ -17,9 +16,7 @@ There are a few core assumptions about each of these entities:
   In our code, this secondary process is ``force_bdss`` itself, invoked with
   the option ``--evaluate``.
 - The DataSources are entities that, given the MCO parameters, provide some
-  numerical result. This result is passed to the KPI calculators.
-- The KPI calculators now compute the final KPIs that are then returned to
-  the invoker MCO.
+  numerical result.
 - The Notification Listener listens to the state of the MCO (Started/New step
   of the computation/Finished). It can be a remote database which is filled
   with the MCO results during the computation (e.g. the GUI ``force_wfmanager``
@@ -35,15 +32,10 @@ The result can be represented with the following data flow
 
 1. The MCO produces and, by means of a Communicator, injects...
 2. ...DataSourceParameters, that are passed to...
-3. one or more DataSources, each performing some computation or data
-   extraction and produces
-4. DataSourceResult, one per DataSource, are then passed (together with the
-   DataSourceParameters) to...
-5. one or more KPICalculators, which perform final data evaluation on the
-   obtained values, eac producing KPIResult...
-6. Whose values are then returned to the MCO via the Communicator.
-7. The KPI values are then sent to the notification listeners with the
+3. one or more DataSources, organised in layers,
+   each performing some computation or data extraction and produces. Layers
+   are executed in order from top to bottom. Results that are classified as
+   KPIs are then returned to...
+4. The MCO via the Communicator.
+5. The KPI values are then sent to the notification listeners with the
    associated MCO parameters values
-
-The resulting pipeline is therefore just two layers (DataSources, then
-KPICalculators).